1. Technical Field
This invention relates to a bearing shell with an oil bore which passes radially through the plain bearing shell to insert oil into the plain bearing shell.
2. Related Art
Typical applications of the generic plain bearing shell are the crankshaft main bearing, the connecting rod bearing or bushings in internal combustion engines. Generic plain bearing shells are known from the DE 10 2005 037 502 A1 or DE 101 63 292 A1, for example.
Typically, two of such plain bearing shells form a plain bearing, wherein the mounted shaft slides on an oil film, which forms on the inside of the plain bearing shell between the shaft itself and the load-bearing surfaces. In order to ensure the formation of this oil film between the load-bearing surface and the inner shaft, oil is inserted through the oil bore in the plain bearing shell, and in particular injected. The oil is distributed in the plain bearing shell and lubricates the load-bearing surfaces, upon which it is driven by the rotating shaft, whereby the oil film is formed, on which the shaft slides.
In addition to the formation of the oil film, the oil cools the plain bearing, whereby it dissipates the heat generated during the operation of the bearing. The ambient operating temperatures are between 90° C. for normal applications up to 210° C. in extreme applications, such as in racing cars. About ¾ of the amount of oil injected in the plain bearing shell is used for cooling.
The oil is injected into the plain bearing shell by means of an oil pump. The oil pump is driven by a motor that drives the vehicle. A part of the power delivered by the engine is required to drive the oil pump. The amount of the power required for driving the oil pump can be reduced by reducing the volumetric flow rate of the oil through the oil bore. With a reduction of the amount of power that is needed to drive the oil pump, engine fuel consumption and therefore the CO2 emissions will be reduced, also.
Some plain bearing shells have oil grooves, by which the oil is distributed inside the bearing shell. The volumetric flow rate is proportional to the surface of the oil groove, so, for the reasons provided above, the aim is to shape the oil groove as low as possible. The plain bearing shell encloses typically an angle of 180° in circumferential direction, so that two plain bearing shells completely surround the shaft to be mounted. The oil groove can go through the entire plain bearing shell so that it also covers an angle of 180° in the circumferential direction. In order to reduce the oil groove surface and therefore the volumetric flow rate of the oil through the oil groove, the angle can be reduced. There are plain bearing shells known having an oil groove with an angle of 150°, and even angles of 120° are tested. However, it has to be taken into account, that the volumetric flow rate through the oil groove is not reduced overly, to ensure a sufficient cooling.
By reducing the angle of the oil groove the required amount of oil has to be inserted into the plain bearing through a reduced surface and the oil has to be distributed over a larger surface in order to ensure an unobjectionable mounting. This leads to an increasing amount of the oil emerging from the bearing side and being lost. Usually a significantly larger amount of oil is inserted into the bearings as actually needed to ensure the unobjectionable mounting of the shaft and to prevent a failure. In order to procure the necessary volumetric flow rate, the engine must provide a higher power to the oil pump, which increases the fuel consumption of the engine.